#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;
#include<vector>
class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int len = nums.size();
        int count[100000] = { 0 };
        for (int i = 0; i < len; i++)
        {
            count[nums[i]]++;
        }

        for (int i = 0; i < len; i++)
        {
            if (count[nums[i]] == 2)
            {
                return nums[i];
            }
        }
    }
};

int main()
{
	//gugu::test_vector2();
	return 0;
}